Engineered immune cells that normally calm inflammation reduced allergic airway reactions in mice, suggesting that a technology developed for cancer could eventually be used to treat severe allergies.

Allergic reactions are common, but for some people they can be dangerous. Peanuts, shellfish, pollen and other normally harmless substances can trigger anything from itching and hives to severe breathing problems and, in the most serious cases, life-threatening anaphylaxis.

Current treatments can reduce these reactions, but they do not always solve the underlying problem: an immune system that reacts too strongly to something it should tolerate. Allergen immunotherapy attempts to change that response by exposing patients to gradually increasing amounts of the substance that triggers their allergy. But this process can take a long time and is not suitable for every patient. Other treatments, including antibody drugs that block key parts of the allergic response, require repeated injections.

A new study points to a different strategy. Instead of repeatedly giving a drug or allergen, it uses the patient’s own immune cells as a treatment. The cells are engineered to recognize a specific allergen and then suppress the immune response around it. The approach adapts a technology best known for cancer treatment: CAR-T therapy. In mice, the engineered cells reduced inflammation and improved breathing after allergen exposure, raising the possibility of using CAR-T technology to treat allergies by restoring immune tolerance.

From Cancer Killer to Immune Regulator

As described in the book CAR-T: A New Cure for Cancer, Autoimmune and Inherited Disease , one main idea lies at the heart of CAR-T therapy: immune cells can be given new instructions. The technology has become an important treatment for certain blood cancers, where engineered cells are programmed to find and destroy cancer cells. The book also describes the broader potential of CAR-T as a platform that could be adapted for diseases beyond cancer.

The new study uses the same concept but gives the cells a different job. Instead of using immune cells that attack their targets, the treatment uses regulatory T cells, which naturally help keep the immune system under control. These cells prevent immune reactions from becoming too strong or continuing after they are no longer needed.

The problem is that ordinary regulatory T cells do not know which immune response to suppress. The new approach gives them that direction. The cells receive a new receptor that recognizes a protein from birch pollen. When they encounter that allergen, they activate and can suppress the immune response around them. The result is a cell that combines targeting and immune suppression in one treatment: it can find the allergen, and it can calm the ensuing inflammation.

Making Birch Pollen the Target

Birch pollen was chosen as the first test because one of its proteins is a major trigger of birch pollen allergies. The engineered cells were designed to recognize the birch pollen protein. When they encountered the allergen, they became activated and suppressed allergic immune activity.

Broadly suppressing the immune system can leave people more vulnerable to infections and other problems. A treatment that acts only when it encounters a particular allergen could potentially control the unwanted immune response without shutting down the body’s defenses more generally.

Reduced Allergic Reactions in Mice

The strongest test came in mice that had been sensitized to birch pollen. After receiving the engineered cells, the animals showed less inflammation in their lungs when exposed to the allergen. The engineered cells also moved into the lungs and nearby immune tissues, where they could encounter the allergic response.

The treatment also changed the broader allergic response. Levels of the allergy-associated antibody IgE were reduced, as was production of one of the immune signals involved in allergic inflammation. The treated mice also had fewer of certain inflammatory cells associated with allergic disease.

The effect went beyond simply blocking one symptom; instead, the engineered cells changed the immune environment that produces the allergic reaction.

A New Direction for CAR-T

The first generation of CAR-T treatments was designed largely around one goal: finding and destroying cancer cells. But the underlying technology does not require an engineered immune cell to be destructive. It can also be used to give immune cells new instructions for controlling inflammation.

That opens a very different field of possibilities, suggesting that the same approach could eventually be adapted to other allergens. It could also provide a way to target other immune reactions in which the body’s defenses are attacking something they should tolerate.

There is still a long way to go before these cells could become an allergy treatment. The current study was performed in mice, and the safety, durability and practicality of using engineered regulatory T cells in people will need to be established. If the approach succeeds in humans, it could move allergy treatment beyond managing reactions toward something more ambitious: teaching the immune system to stop reacting to the substances it should have tolerated all along.